How to Inner Join using Spring Boot JPA / Hibernate in Repository? - spring

I am currently learning spring boot , hibernate and Spring Boot JPA
I developing a Classroom App for coaching centers and institutes .
In it, students enrolled to multiple courses in a single institute
The Student Entity class :
#Entity
#Table(name = "student")
public class Student {
private String name;
private String dob;
private String gender;
private String address;
private String email;
private Integer mobile;
private String joined;
private Integer instID;
#Id
private String studentid;
getters and setters()....
}
Course Table Entity class
#Entity
#Table(name = "courses")
public class Course {
private String name;
private String description;
private String logo;
private String start;
private String end;
private Integer fee;
#Id
private String courseid;
private Integer instID;
getters and setters();
}
Enrolled Classes Table's Entity class
public class EnrolledCourses {
#Id
String enrollID;
String courseid;
String studentid;
Date joined;
getters and setters()...
}
JPA Repository
#Repository
public interface StudentRepository extends CrudRepository<Student, String> {
Student findTopByInstIDOrderByStudentidDesc(int instID);
}
#Repository
public interface CourseRepository extends CrudRepository<Course,String> {
}
#Repository
public interface EnrolledRepository extends CrudRepository<Course,String> {
}
My Need
Now I am retrieving enrolled students for a given course in a given institute... by using this MySQL query
SELECT
`enrolled_courses.enrollID`,
`student.name`, `student.studentid`
FROM `enrolled_courses`
INNER JOIN `student`
WHERE
`enrolled_courses.studentid` = `student.studentid`
AND
`student.instID` = 13
AND
`enrolled_courses.courseid` = '13I01C' ;
Now I need to implement this Inner join query in CourseRepository (or enrolledstudent repo)
How to achieve this ?
Please guide me

If we use hibernate mapping in EnrolledCourses entity like
#Entity
public class EnrolledCourses {
#Id
String enrolledId;
#ManyToOne
Student student;
#ManyToOne
Course course;
Date joined;
getters and setters()...
}
from the above mappings without using any SQL queries, you can retrieve all student who comes under a particular course
By using the method in the interface
#Repository
public interface EnrolledRepository extends CrudRepository<EnrolledCourses,String> {
List<EnrolledCourses> findByCourse_CourseId(String courseId);
}
if we have some relations between the entities we can easily retrieve all the fields using Jpa.

Related

How to use Spring Boot CRUD API to insert data in multiple tables using one POST endpoint

How can a data be inserted using single POST endpoint in multiple tables. For example there are two tables
1. Employee
2. Department
These two tables have a primary key and foreign key relationship.
How to achieve data insertion in two tables using a single POST endpoint ?
Ok I see what you want.... your entities have to look like this...
You have to create a one to one relationship something like this:
Department entity:
#Entity
#Table
#Data
public class Department {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
private String name;
private String description;
}
Employee entity:
#Entity
#Table
#Data
public class Employee {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
private String name;
private String email;
private String address;
#OneToOne(cascade = CascadeType.ALL)
#JoinColumn(name = "department_id", referencedColumnName = "id")
private Department department;
}
And than you can add Data on Startup like this:
#Component
public class DBSeeder implements CommandLineRunner {
#Autowired
private EmployeeRepository repository;
#Override
public void run(String... args) throws Exception {
Department dep1 = new Department();
dep1.setName("Demolition");
dep1.setDescription("Do demo");
Employee emp1 = new Employee();
emp1.setName("John Rambo");
emp1.setEmail("john.rambo#demolition.com");
emp1.setAddress("Demolition Av. 5");
emp1.setDepartment(dep1);
this.repository.save(emp1);
}
}
#Repository
public interface EmployeeRepository extends CrudRepository<Employee, Long> {
Employee save(Employee employee);
}
Do you also ask how the entity objects have to look like?

How can I add a tenant condition to Spring Data JPA Default and Dervied Queries

I have a Springboot Application with Repositories having Spring Data JPA Queries like findOne, findAll and also derived ones like findByID or findByName etc.
What I want to achieve is multitenancy. All entities have an "account_id" column which holds the tenant.
How do I add a filter like "account_id" to all the queries metioned above without using derived queries that contains those name slike findIdAndAccountid (which would be findone)
#Repository
public interface CategoryRepository extends JpaRepository<Category, Long> {
Category findByName(String name);
}
Here's the corresponding entity
#Entity
#Table(name = "unit")
#Data
public class Unit {
#Id
#GeneratedValue(strategy=GenerationType.AUTO)
private Long id;
private String name;
#Column(name = "account_id")
private Long account_id;
}
I know most people use schemas as tenant separation but that's impossible for me. Is there a way (I didn't find one) to add such a tenant filter condition on those queries without writing NamedQueries or using DerivedQueries. An elegeant solution like annotate the repository or entity or maybe the queries that all queries should add the additional filter "account_id"?
You can add Where clause on your Entity classes (Didnt had time to test )
#Entity
#Table(name = "unit")
#Data
#Where(clause = "account_id= :account_id")
public class Unit {
#Id
#GeneratedValue(strategy=GenerationType.AUTO)
private Long id;
private String name;
#Column(name = "account_id")
private Long account_id;
}
Update and Solution
1. Create a Filter & FilterDef on the entity like so
#FilterDef(name="accountFilter", parameters=#ParamDef( name="accountId", type="long" ) )
#Filters( {
#Filter(name="accountFilter", condition=":accountId = account_id")
} )
public class Category {
#Id
#GeneratedValue(strategy=GenerationType.AUTO)
private Long id;
private String name;
#Column(name = "account_id")
private Long account_id;
}
enable filtering in the controller by autowiring entitymanager, writing a method to enable the filter and activate the filter in #ModelAttribute for each request
#RestController
#RequestMapping(path = "/categories",produces = MediaType.APPLICATION_JSON_VALUE )
public class CategoryController {
private final CategoryRepository repository;
#Autowired
private EntityManager entityManager;
CategoryController(CategoryRepository repository) {
this.repository = repository;
}
private void activateFilter() {
Session session = entityManager.unwrap(Session.class);
Filter filter = session.enableFilter("accountFilter");
filter.setParameter("accountId", Long.valueOf(TenantContext.getCurrentTenant()));
}
#ModelAttribute
public void initFilter() {
activateFilter();
}
... your rest methods here
}

Spring boot MongoDb complex query

I have been learning myself MongoDB implementation in Spring Boot.
However, I came into a problem with complex queries.
I cannot find any right solution for how to implement complex queries to MongoDB from Spring boot.
I am querying the database with MongoRepository interface implementation.
Let's say that I have three collections:
Person - 1 Person can have many Pets.
Pet - 1 Pet can have 1 PetToy and 1 Person who owns him.
PetToy - 1 PetToy can belong to 1 Pet.
POJO classes are bellow
What do I want to achieve?
I want to make a query, which would be returned me a Person, whose Pet has a Toy (PetToy) with the name "Teddy".
I could not have found a way how to do it. Furthermore, is it the best practice to even use such complex queries, or is it better to write more of little ones in MongoDB?
POJOs:
#Document
#Data
#ToString
public class Person {
#Id
private String id;
private String firstname;
private String lastname;
private int age;
#DBRef
private Pet pet;
}
#Document
#Data
#ToString
public class Pet {
#Id
private String id;
private String name;
private int age;
#DBRef
private List<PetToy> toys;
}
#Document
#Data
#ToString
public class PetToy {
#Id
private String id;
private String name;
}
I have tried to use MongoRepositories; however, I was not able to make the complex query.
How can one write such a query to a MongoDB from Spring Boot?
Thank you very much in advance.
If you can use embedded attributes, the class model should be:
#Document
#Data
#Builder
public class Person {
#Id
private String id;
private String firstName;
private String lastName;
private int age;
private List<Pet> pets;
}
#Data
#Builder
public class Pet {
private String name;
private int age;
private List<PetToy> toys;
}
#Data
#Builder
public class PetToy {
private String name;
}
The repository with the method that achieves what you want:
public interface PersonRepository extends MongoRepository<Person, String> {
List<Person> getByPetsToysName(String name);
}
The getByPetsToysName method basically navigate between Person's attributes Person->pets->toys->name. More info here.
An example
#Configuration
#EnableMongoRepositories
public class TestMongo implements CommandLineRunner {
private final PersonRepository repository;
public TestMongo(PersonRepository repository) {
this.repository = repository;
}
#Override
public void run(String... args) throws Exception {
repository.save(Person.builder()
.firstName("John")
.lastName("Doe")
.age(20)
.pets(Stream.of(Pet.builder()
.name("Ursa")
.age(1)
.toys(Stream.of(PetToy.builder()
.name("Teddy")
.build())
.collect(Collectors.toList()))
.build())
.collect(Collectors.toList()))
.build());
repository.save(Person.builder()
.firstName("Phillip")
.lastName("Larson")
.age(21)
.pets(Stream.of(Pet.builder()
.name("Bella")
.age(5)
.toys(Stream.of(PetToy.builder()
.name("Lolo")
.build())
.collect(Collectors.toList()))
.build())
.collect(Collectors.toList()))
.build());
List<Person> persons = repository.getByPetsToysName("Teddy");
System.out.println(persons.size());
List<Person> persons1 = repository.getByPetsToysName("Lolo");
System.out.println(persons1.size());
}
}
Logs:
find using query: { "pets.toys.name" : "Teddy" } fields: Document{{}} for class: class Person in collection: person
If you want more complex queries you can to take a look at the Spring Data MongoDB docs.

i'm getting null value in a child table as a foreign key of parent table using spring data rest or spring data jpa accosiation

enter image description here In this image first address for empId 1 and last two records are empid 2 (empid 2 haveing to address)
file:///home/user/Pictures/fk.png
#Entity
#Table(name = "Employee")
public class Employee {
#Id
#GeneratedValue
private Integer id;
private String name;
private Integer sal;
#OneToMany(cascade = CascadeType.ALL,mappedBy="employee")
private List<Address> addresses;
//getter setter
Child entity
#Entity(name="Address")
public class Address {
#Id
#GeneratedValue
private Integer aid;
private String city;
private String state;
#ManyToOne
#JoinColumn(name="id")
private Employee employee;
//getter setter
Repository
#Repository
#RepositoryRestResource(path="employee")
public interface EmployeeRepo extends JpaRepository<Employee,Integer> {
}
Input from RestClient
{
"name":"rdhe",
"sal":"20000",
"addresses":[{
"city":"hyd",
"state":"ts"
}]
}
if i use spring data jpa then code will be
// jpa Repository
public interface EmployeeRepo extends JpaRepository<Employee,Integer> {
}
// EmployeeServer class
#Service
public class EmployeeService {
#Autowired
EmployeeRepo employeeRepo;
public void saveEmployee(Employee employee){
employeeRepo.save(employee);
}
}
// controller
#RestController
public class EmployeeController {
#Autowired
EmployeeService employeeService;
#PostMapping(path="/save")
public void saveEmp(#RequestBody Employee employee){
employeeService.saveEmployee(employee);
}
}
if i'll use spring-data-rest at that time no need to create employeeService and controller class
I was getting the same problem until JsonManagedReference came to my rescue.
Try changing your entities to include them like this:
In the Employee Entity:
#OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY, mappedBy ="employee")
#JsonManagedReference
private List<Address> addresses;
In the Address Entity:
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "id", nullable = false, updatable = false, insertable =true)
#JsonBackReference
private Employee employee;
I was not able to find why it works this way, so please let me know if you come to know :)
It is probably due to the fact that your mentioning #JoinColumn(name="id"). The name attribute in #JoinColumn defines the name of the foreign key field in the child table. Since you are specifying foreign key column as id on hibernate, it could be the issue. Please update it to the same name(ie fk_empid) as specified in database, it should work...

How to search through array in Spring Boot CrudRepository

Say, I have the following entity class:
Person.java
#Entity
public class Person {
#Id
private String name;
private String[] cars;
// Constructor, getters and setters
}
And the repository:
PersonRepository.java
public interface PersonRepository extends CrudRepository<Person, String> {
// this is unclear!
List<Person> getAllByCars...(String car)
}
Is there a method that returns all persons, whose car array contains one given car (the String parameter above)?
For me, it seems that all supported JPA keywords can only deal with single elements, but not with arrays.
Thanks for help!
Ideally, You should declare cars as a separate Entity like this
#Entity
public class Person {
#Id
private String name;
private List<Car> cars;
// Constructor, getters and setters
}
If not you should change Array to List at the least.
change
private String[] cars;
to
#ElementCollection
private List<String> cars;
Then You have to write a Query like this
#Query("select p from Person p WHERE :car in elements(p.cars)")
List<Person> getAllByCars...(#Param("car") String car)
I'm guessing at how you are currently storing the cars information and suggesting a possible solution:
#Entity
public class Car {
#Id
private String name;
#Column
private String person_name;
}
public interface CarRepository extends JpaRepository<Car, String> {
//Result will have all cars with the person_name identifying the Person #Entity
List<Car> findByName(String name);
}

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